ECL (emitter-coupled logic) is a type of integrated circuit logic which uses bipolar transistors. As compared to other logic families, such as TTL (transistor-transistor logic), or CMOS (complementary metal-oxide semiconductor) logic, ECL circuits have higher switching speeds, but consume a large amount of power. ECL circuits have the advantage of high speed over other logic families because the voltage swing between high and low logic states is relatively low, and may be less than one V.sub.BE, where a V.sub.BE is the forward biased base-emitter diode voltage drop of a corresponding bipolar transistor.
Typically, in an integrated circuit that receives ECL signals, the ECL signals are buffered and level converted to CMOS or BICMOS logic levels before a logic operation can be performed. BICMOS circuits are so called because they include both bipolar and CMOS transistors in the same circuit. The ECL signals are level converted to CMOS or BICMOS logic levels to provide better operating margins in order to account for process variations, temperature, and noise. Multiplexing, logic operations, and other digital signal processing is performed on the level converted logic signals. In applications requiring very high speeds, such as workstations or super computers, valuable time is lost by doing a level conversion from one logic family to another before the signal processing is performed.